Sustainability has to do with our future, and this involves many different areas of our lives and society. In the video below, you can find a pretty good summary of the objectives of sustainable development.

cull (kʌl)
vb (tr)
1. to choose or gather the best or required examples
2. (Agriculture) to take out (an animal, esp an inferior one) from a herd3. (Agriculture) to reduce the size of (a herd or flock) by killing a proportion of its members
4. (Horticulture) to gather (flowers, fruit, etc)
5. to cease to employ; get rid of
n
6. the act or product of culling
7. (Agriculture) an inferior animal taken from a herd or group

So, a cull is an act of killing a proportion of animals in order to reduce their population.

What is a badger ? If you have seen Fantastic Mr. Fox, you have met Mr. Badger :

And where is West Somerset ? Somewhere on the western coast of England :

Now you can watch this report about the badger cull in West Somerset :